1. Field of the Invention
Embodiments of the present invention relate to an injection stretch blow molding method and apparatus for producing internally threaded containers.
2. Description of the Related Art
Injection stretch blow molding (ISBM) is a technique used for creating various containers such as plastic bottles. The ISBM process is performed with an ISBM machine that first injection molds a resin into a plurality of parisons of desired shapes, conditions the parisons in preparation for stretch blow molding, stretch blow molds the parisons into the final molded articles, and then ejects the molded articles from the ISBM machine. ISBM machines generally include two types, 3-stage or 4-stage. The 4-stage ISBM machines may broadly comprise an injection station for injection molding the resin into the parisons, a conditioning station for processing the parisons (e.g., applying heat and/or cooling to the parisons), a stretch blow station for stretch blow molding the parisons into the final molded articles, an ejection station for ejecting the molded articles from the ISBM machine, and a rotation plate for transferring the parisons and the molded articles between the stations of the ISBM machine. The 3-stage ISBM machine differs from the 4-stage machine in that the 3-stage machine will not include a conditioning station.
Typically, the molded articles formed by the ISBM machine are containers. Such containers are often manufactured in the form of plastic bottles, with such bottles having a main body and a neck extending up from the main body. The necks will include threaded exterior surfaces for securing lids or caps to the containers. The lids or caps serve to seal the containers and their contents. In certain instances, it would be preferable to manufacture containers that include necks with threaded interior surfaces, such that lids or caps could be secured to the container via the threaded interior surfaces. Such internally threaded containers may be beneficial because they can create better seals and/or can minimize or alleviate leakages. Additionally, containers with internal threads may provide for smooth outer surfaces, which can be more aesthetically pleasing.
Thus, it would be desirable to have an ISBM machine and method for producing molded articles (e.g., containers) with internal threads, such that the molded articles can be sealed via the internal threads.